The binding of fibrinogen and fibrinogen degradation products to the erythrocyte membrane and its relationship to haemorheology.

A study has been made of the binding of fibrinogen to erythrocyte membranes. The amount of fibrinogen bound is found to be proportional to the concentration in the suspending phase (up to 10 g/l) and to be unaffected by other plasma proteins or calcium ions (up to normal concentrations). The binding is also unaffected by temperature (between 4 and 37 degrees C). However it is sensitive to both pH and ionic strength variation. A similar study of the major fibrinogen degradation products (FDP) produced by plasmin shows that these all bind to red cell membranes but by different amounts. A model based on these data is suggested for the positions of the binding regions on the fibrinogen and FDP molecules and is used to explain their influence on rouleaux formation and on the flexibility of the erythrocyte.